Doesn't really answer my question regarding its legality. Also, this is not a solution guide to a textbook like say calculus. This is a solution guide to actual standardized tests where detailed solutions are incredibly helpful for self study. You're thinking of, let's say, a physics textbook and the professor assigns homework and students go online and just copy my answers. This is not what's happening at all. This is a test that students need to continue their studies, so it's in their best interest to deeply evaluate their mistakes.

I am not sure. That answer depends on the overall legality I suppose. If my students find it useful, I would like to get it in the hands of more people, for a fee if the market merits, but free is fine as well.